This invention relates generally to the field of firearms and specifically to the field of gun barrels for automatic and semiautomatic firearms.
A gun barrel is a very high precision part which guides the bullet until it leaves the barrel. In order for a barrel to perform to its full accuracy it must be allowed to vibrate freely and be unaffected by outside forces, such as sling tension.
On the outside of a normal gun barrel near the firing mechanism is a circular shoulder which is used to pull the gun barrel into tight engagement with the receiver that receives the gun barrel, and other parts. Typically, a nut, that has a shoulder matching the rib of the gun barrel, is used to hold and adjust the gun barrel so that when the nut is tightened the gun barrel is pulled into position and held there. There is also a gas tube which starts at the outer tip of the gun barrel and carries the expanding gas from the exploding gun powder back to the operating mechanism of the gun to work a piston to open the bolt, throw out the used cartridge, pick up a new cartridge, and close the bolt again. This feature permits automatic firing. The gas tube is kept very close to the barrel and actually passes through the nut which holds the barrel in place. Unfortunately, the threads on the receiver, on which the nut turns, can start at any rotational position. For that reason the hole in the nut for the gas tube cannot be aligned with any certainty unless it is drilled separately for each gun. Machining for an accessory rail used in target shooting or sling swivel must also be done individually for each gun. The alternative is to provide a series of holes all the way around the nut and line one of them up. Neither is a very good solution, particularly since it may be necessary to back off the nut slightly from its full tight position to line up a hole for the gas tube.
A second problem with the way guns are currently constructed is that the mounting for the end of the sling, by which the gun is carried and steadied to fire, is on the outer end of the gun barrel. That means that when the gun is being fired, the tension of the sling which is used to steady the gun also tends to bend the barrel slightly in the direction of the force on the sling. Since the force on the sling is in different directions, depending on whether the gun is being fired from a standing position, a sitting position, or a prone position, the gun barrel will bend in different directions and throw the accuracy off in different ways for the different positions. In any case, the gun barrel should not bend but should be totally straight and allowed to vibrate freely.
The device of my invention overcomes these problems by virtue of its unique and simple design. I am aware of no prior art device which performs the function of my proposed invention.
For example U.S. Pat. No. 3,877,167 (Keppeler) shows neither a gas tube nor any part that needs to be aligned in the way that a gas tube must be aligned. However, a gun barrel with two separate nuts is shown. Referring to reference character 3 of the patent it may be seen that a breach with threads to receive a gun barrel is shown. Also shown is a keyway for receiving pin 9 in the receiver. The extent to which the gun barrel is screwed into the breach is not critical so it could be rotationally adjusted to the correct position after which nut 10 could be screwed into the receiver to force breach 5 into engagement with receiver 8. There is no disclosure suggesting that this patent function in the manner of the present invention nor that it have the structure of the invention. In particular the gun barrel shown does not have a circular rib so the mode of action is different.
Other references include U.S. Pat. No. 1,065,341 (Browning), U.S. Pat. No. 1,628,798 (Nelson), U.S. Pat. No. 1,172,714 (Johnson), U.S. Pat. No. 2,736,117 (Clarkson) U.S. Pat. No. 2,763,118 (Clarkson), U.S. Pat. No. 4,674,217 (Matievich), U.S. Pat. No. 3,842,527 (Low), U.S. Pat. No. 4,920,679 (Sarles), and U.S. Pat. No. 529,455 (Marlin).